Turbine

ABSTRACT

The invention relates to a turbine ( 6 ), especially a gas turbine. According to the invention, a sealing element ( 44 ) with a receiving area ( 50 ) is provided for sealing the guide blades ( 18 ) which are adjacent to each other in the peripheral direction ( 36 ) of the turbine ( 6 ). The foot plates ( 21 ) of the guide blades ( 18 ) extend into aid receiving area. The edge area of the foot plates ( 21 ) does not have to be reinforced compared to a conventional seal, which enables the entire foot plate to be cooled homogeneously. A closed cooling system ( 62 ) can therefore be used for cooling, especially with steam.

[0001] The invention relates to a turbine, in particular a gas turbine.

[0002] In a turbine, in particular in a gas turbine of a turbo set of apower station for energy generation, a hot gas is led through theturbine, with a result that a shaft having moving blades arranged on itis driven. This shaft is connected, as a rule, to a generator for thegeneration of energy. The moving blades extend radially outward.Stationary guide vanes are arranged in the opposite direction, that isto say radially from the outside inward. As seen in the longitudinaldirection of the turbine, the guide vanes and the moving blades engageone into the other in a tooth-like manner. The turbine, as a rule, has aplurality of turbine stages, a guide vane ring being arranged in eachstage, that is to say a plurality of the guide vanes are arranged nextto one another in the circumferential direction of the turbine. Theindividual guide vane rings are arranged successively in the axialdirection. The flow path of the hot gas through the turbine isdesignated hereafter as the gas space.

[0003] The guide vanes each comprise a vane leaf which extends radiallyinto the gas space and is attached to a foot plate, via which the guidevane is fastened to what is known as a guide vane carrier. Theindividual foot plates of the guide vanes form an essentially closedsurface and outwardly delimit the gas space. In order to achieve assmall leakage gaps as possible between the individual foot plates, sealsare provided, as a rule, between the individual foot plates.

[0004] In a conventional seal variant, the foot plate edge region ismade thickened, particularly in the case of foot plates adjacent to oneanother in the circumferential direction, an end-face groove beingworked into the thickening. For sealing, a common sealing sheet isintroduced into mutually opposite grooves of adjacent foot plates.

[0005] The massive construction of the edge region in which the groovefor the sealing sheet is arranged presents problems in terms of thethermal load on the foot plate. On account of the high temperatures inthe turbine, the foot plates are normally cooled by means of a coolant.In this case, special cooling measures have to be taken for the massiveedge region, so not as not to give rise to any excessive thermalstresses between the massive edge region and the relatively thin plateregion of the foot plate.

[0006] This problem is aggravated when a closed cooling circuit, forexample a closed steam cooling circuit, is provided for cooling, sincethis does away with the possibility of guiding through the massive edgeregion cooling bores through which, for example, cooling air can flow.Instead, in the case of a closed cooling circuit, such bores have to beproduced as blind holes, the cooling effect naturally being low in thiscase, since the cooling medium will scarcely flow through the blind holeto a sufficient extent.

[0007] In a further seal variant, the grooves and the sealing sheet areset back from the hot-gas side located on the gas-space side and anundercut is introduced into the massive edge region below the sealingelement. Here, too, there is then again the problem of the coolantflowing through this undercut to a sufficient extent. A third sealvariant, according to which cooling ducts are introduced into the bodyof the foot plate itself, is complicated in production terms. Inparticular, here, there is the problem that, in order to form thecooling ducts during the casting of the foot plate, a core, which ispositioned via spacers, also has to be cast in. The core and the spacersare removed by means of suitable measures after casting, so that thecavities formed thereby can be used as cooling ducts. However, there isa connection of the cooling ducts to the outside via the cavity producedby the spacers, so that a closed cooling circuit can be implemented onlywith difficulty.

[0008] The object on which the invention is based is, in a turbine, todesign the seal between adjacent guide vanes suitably for simplecooling.

[0009] The object is achieved, according to the invention, by means of aturbine, in particular by means of a gas turbine, with a gas space andwith a number of guide vanes which each have a foot plate and a vaneleaf extending radially from the foot plate into the gas space, asealing element with a reception region, into which the foot platesextend, being provided in each case between the foot plates of adjacentguide vanes.

[0010] The fundamental idea of this configuration is to be seen in thereversal of the conventional sealing principle, in which a sealing sheetis introduced into corresponding grooves of the foot plates. To beprecise, this necessarily requires a reinforcement of the edge of thefoot plates in the groove region, thus ultimately leading to the coolingproblems. In this case, in a reversal of this sealing principle, thesealing sheet is not inserted into the foot plates, but, instead, thefoot plates are introduced into the sealing element. This avoids theneed for a reinforcement of the edge region of the foot plate.Coolability is therefore simplified and the foot plate is cooledhomogeneously in all regions, so that no thermal stresses occur.

[0011] In a preferred design, the sealing element is designed with anH-shaped cross section with two longitudinal limbs connected via atransverse limb, there being formed between the longitudinal limbs tworeception regions which are separated from the transverse limb and intowhich the foot plates of adjacent guide vanes extend in each case. Thesealing element thus partially covers the adjacent foot plates with itstwo longitudinal limbs, so that, in addition to the sealing property,the foot plates are held by the sealing element.

[0012] In view of assembly requirements during the production of theturbine, the sealing element is arranged preferably between guide vanesadjacent to one another in the circumferential direction of the turbine.

[0013] According to a preferred refinement, the foot plates each have aside edge bent away from the gas space, in particular radially outward,the sealing element being arranged between two side edges of adjacentguide vanes. The effective sealing height of the seal is therebyincreased, without the plate thickness of the foot plate beingincreased. The two bent-away side edges of the foot plates in this casecome to bear, in particular, on the transverse limb of the H-shapedsealing element.

[0014] In order to achieve homogeneous cooling and consequently avoidthermal stresses, the side edge has substantially the same materialthickness as the remaining foot plate.

[0015] In order to prevent the sealing element from projecting into thegas space, the front side of the foot plate, said front side beingdirected toward the gas space, has, in the region of the sealingelement, a bearing surface which is set back from the gas space and onwhich the sealing element lies. Preferably, at the same time, thesealing element is flush with the foot plate.

[0016] In an expedient refinement, there is, for cooling the sealingelement, a flow path in the form of a leakage gap for air between thesealing element and the foot plates. There is therefore no desire tohave absolute leaktightness, in order to keep low the thermal load inthe region of the sealing element and at the side edges of the footplate. As a rule, the outside space around the gas space in a turbine iskept at a higher pressure than the gas space, so that air enters the gasspace from outside via the leakage gap and the outflow of hot gas fromthe gas space is avoided.

[0017] In a particularly advantageous embodiment, a closed coolingsystem, through which a coolant is capable of flowing, is arranged inthe rear region of the foot plates which faces away from the gas space,that is to say in the outside space. The coolant is in this case, inparticular, steam. Alternatively, the coolant used is also a liquid,such as water, or another gas, such as air or hydrogen. Such a closedcooling system allows an effective, directional and homogeneous coolingof the foot plates and of the entire guide vanes.

[0018] Preferably, at the same time, the coolant is capable of flowing,in particular directly, over the rear side of the foot plates whichfaces away from the gas space, so that direct heat exchange takes placebetween the coolant and the foot plate.

[0019] In order to achieve an effective cooling of the foot plates, aninflow duct for the coolant is formed between an outer guide sheet and abaffle sheet, the baffle sheet being arranged between the outer guidesheet and the foot plate and having flow orifices toward the foot plate,and a return-flow duct for the cooling medium being formed between thebaffle sheet and the foot plate. A closed cooling system, which has ahigh cooling action, is consequently implemented in a simple way. Duringoperation, the coolant is supplied via the inflow duct and is guided athigh velocity onto the foot plate via the, in particular, nozzle-likeflow orifices in the baffle sheet, so that intensive heat exchange takesplace between the coolant and the foot plate. The heated coolant issubsequently discharged in the return-flow duct.

[0020] Preferably, the baffle sheet is supported on the foot plate via asupporting element, so that the baffle sheet is held at a defineddistance from the foot plate.

[0021] For simple fastening, preferably the baffle sheet is fastened tothe bent-away side edge of the foot plate and the guide sheet isfastened, in particular, to the baffle sheet.

[0022] In order to achieve a simple mounting of the foot plates and atthe same time good sealing of the foot plates both in thecircumferential direction and in the axial direction between adjacentturbine stages, preferably the sealing element described is provided forsealing in the circumferential direction and a further sealing elementis provided for sealing in the axial direction. Depending on thedirection, therefore, and particularly for assembly reasons, differentlydesigned sealing elements are used.

[0023] The further sealing element connects the foot plates to oneanother in a staple-like manner, preferably on their rear sides facingaway from the gas space. The essential advantage is in this case to beseen in the staple-like configuration of the further sealing elementwhich spans the two foot plates. The further sealing element is in thiscase designed to be elastic, in particular in a plurality of directions,so that, under thermal expansions, it follows the foot plates, withoutopening up a gap. The sealing by the further sealing element istherefore largely unaffected by thermal expansions.

[0024] Exemplary embodiments of the invention are explained in moredetail below with reference to the drawing, in which, in each case in ahighly diagrammatical illustration,

[0025]FIG. 1 shows a turbine plant,

[0026]FIG. 2 shows the sealing region between two foot plates adjacentto one another in the circumferential direction of the turbine, in aconventional embodiment,

[0027]FIG. 3 shows the sealing region in a configuration according tothe invention, and

[0028]FIG. 4 shows a seal provided, in particular, for foot platesarranged next to one another in the axial direction of the turbineplant.

[0029] According to FIG. 1 a turbine plant 2, in particular a gasturbine plant of a turbo set for a power station for energy generation,comprises a combustion chamber 4 and a turbine 6 which is arrangeddownstream of the combustion chamber 4 in the longitudinal or axialdirection 8 of the turbine plant 2. The turbine 6 is illustrated, cutaway, in a part region, so that it is possible to look into the gasspace 12 of the turbine 6. The flow path of a hot gas HG through theturbine 6 is designated as the gas space 12.

[0030] During operation, the combustion chamber 4 is supplied via a gassupply 14 with a fuel gas BG which is burnt in the combustion chamber 4and which forms said hot gas HG. The hot gas HG flows through theturbine 6 and leaves the latter as cold gas KG via a gas discharge line16. The hot gas HG is guided in the turbine 6 via guide vanes 18 andmoving blades 20. In this case, a shaft 22, on which the moving blades20 are arranged, is driven. The shaft 22 is connected to a generator 24for the generation of electric energy.

[0031] The moving blades 20 extend radially outward from the shaft 22.The guide vanes 18 have a foot plate 21 and a vane leaf 23 fastened tothe latter. The guide vanes 20 are fastened outwardly to the turbine 6via their foot plate 21 in each case on what is known as a guide vanecarrier 26 and extend radially into the gas space 12. As seen in thelongitudinal direction 8, the guide vanes 18 and the moving blades 20engage one into the other in a tooth-like manner. A plurality of movingblades 20 and of guide vanes 18 are in each case combined to form aring, each guide vane ring representing a turbine stage.

[0032] In the exemplary embodiment of FIG. 1, the second turbine stage28 and the third turbine stage 30 are illustrated by way of example.

[0033] The foot plates 21 of the individual guide vanes 18 arecontiguous to one another both in the axial direction 8 and in thecircumferential direction 32 of the turbine 6 and outwardly delimit thegas space 12.

[0034] The foot plates 21 adjacent to one another are sealed relative toone another, in order to keep leakage gaps 34 between them as small aspossible.

[0035] According to a conventional seal variant for two foot plates 21arranged next to one another in the circumferential direction 32, thelatter have a thickened edge region 36, as shown in FIG. 2. Grooves 40which are located opposite one another and into which a common sealingsheet 42 is inserted are worked into the end faces 38 of the edgeregions 36 of adjacent foot plates 21. This sealing principle, accordingto which the foot plates 21 receive a sealing element in the form of asealing sheet 42, necessarily requires the reinforced edge region 36. Asa rule, this edge region 36 has a thickness Dl higher by the factor 3 tothe factor 5 than the thickness D2 of the remaining foot plate 21.

[0036] These different material thicknesses in the edge region 36 andthe remaining foot plate 21 lead to problems in terms of a uniform andhomogeneous cooling of the foot plates 21, so that there is a risk ofthermal stresses.

[0037] In order to avoid this problem, according to the proposedpreferred embodiment shown in FIG. 3, the conventional sealing principleis reversed, so that, in this case, the foot plates 21 extend into asealing element 44. The sealing element 44 is designed with an H-shapedcross section and has two longitudinal limbs 46 which are connected toone another via a transverse limb 48.

[0038] The sealing element 44 is therefore designed in the manner of a“double-T girder”. Between the two longitudinal limbs 46 are formed tworeception regions 50 which are separated from the transverse limb 48 andinto which the foot plates 21 extend. Alternatively to the H-shapeddesign, the sealing element 44 has a T-shaped design, that is to saywith only one longitudinal limb 46. In a sealing element 44 of thiskind, the reception spaces formed are open.

[0039] In the region of the sealing element 44, the front sides 52 ofthe foot plates 21, said front sides being oriented toward the gas space12, each have a bearing surface 54 which is set back from the gas space12 and on which one longitudinal limb 56 of the sealing element 44 lies.For this purpose, the foot plate 21 has a step-shaped design in theregion of the sealing element 44. The end regions of the foot plates 21,said end regions adjoining the step, are bent away outward from the gasspace 12 approximately perpendicularly and in each case form a bent-awayor radially extending side edge 56. The side edges 56 of the adjacentfoot plates 21 directly fit snugly against the transverse limb 48. Anincrease in sealing height H is thereby achieved, without the foot plate21 being reinforced in the sealing region. A flow path 58 designed as aleakage gap is formed between the sealing element 44 and at least one ofthe foot plates 21, so that, for example, air from the outside space 60facing away from the gas space 12 can flow via the flow path 58 into thegas space 12 and therefore cools the sealing region, that is to say thesealing element 44 and the side edges 56.

[0040] To cool the foot plates 21, in particular, a closed coolingsystem 62 is provided, which uses preferably steam as a coolant and adetail of which is illustrated in FIG. 3. This closed cooling system 62has an inflow duct 64 and a return-flow duct 66. The inflow duct 64 isformed between an outer guide sheet 68 and a baffle sheet 70 which isarranged between the guide sheet 68 and the foot plate 21.

[0041] The baffle sheet 70 has flow orifices 72 which are designed inthe manner of nozzles, so that the coolant supplied via the inflow duct64 flows over into the return-flow duct 66 along the arrows illustrated.By virtue of the nozzle-like operation of the flow orifices 72, thecoolant is guided at high velocity against the rear side 74 of the footplate 21, so that effective heat transmission between the coolant andthe foot plate 21 is implemented. In order to achieve a uniform actionof the cooling system 62, the baffle sheet 70 is supported against thefoot plate 21 and kept at a distance from the latter via supportingelements 76, for example in the form of weld spots or welded webs. Thebaffle sheet 70 is directly fastened, in particular welded, to the sideedge 56 of the foot plate 21, and the guide sheet 68 is fastened to thebaffle sheet 70.

[0042] For assembly and cooling reasons, the sealing arrangementillustrated in FIG. 3 is provided, in particular, for two guide vanes 18adjacent to one another in the circumferential direction 32. Theillustrated inflow ducts 64 and return-flow ducts 66 therefore extend inthe axial direction 8 of the turbine 6. The foot plates 21 of a guidevane ring are thus sealed relative to one another via the H-shapedsealing element 44. For assembly reasons, this seal is less suitable,albeit possible in principle, for foot plates 21 of successive turbinestages 28, 30, said foot plates being adjacent to one another in theaxial direction 8.

[0043] For the sealing of foot plates 21 adjoining one another in theaxial direction 8, according to FIG. 4 a further sealing element 80 ispreferably provided, which connects the foot plates 21 to one another ina staple-like manner on their rear sides 74. The further sealing element80 is in this case introduced and fastened in grooves 82 which extendessentially radially from the rear side 74 into the foot plates 21. Asillustrated in FIG. 4, the further sealing element 80 is, for example,of U-shaped design with two limbs 86 connected via an arc 84.

[0044] Alternatively to this, the further sealing element 80 is providedwith a wavy structure in the manner of a concertina. The elongateU-shaped configuration or else the configuration with the wavy structurehas the effect that the further sealing element 80 is elastic and allowsall-round movability of the foot plates 21 as a result of thermalexpansion. FIG. 4 also illustrates hooking elements 88 which arearranged on the rear sides 74 and by means of which the guide vanes 18are hooked into the guide vane carrier 26 (cf. FIG. 1).

1. A turbine (6), in particular a gas turbine, with a gas space (12) andwith a number of guide vanes (18) which each have a foot plate (21) anda vane leaf (23) extending radially from the foot plate into the gasspace (12), a sealing element (44) with a reception region (50), intowhich the foot plates (21) extend, being provided in each case betweenthe foot plates (21) of adjacent guide vanes (18).
 2. The turbine (6) asclaimed in claim 1, in which the sealing element (44) is designed withan H-shaped cross section with two longitudinal limbs (46) connected viaa transverse limb (48), there being formed between the longitudinallimbs (46) two reception regions (50) which are separated from thetransverse limb (48) and into which the foot plates (21) of adjacentguide vanes (18) extend in each case.
 3. The turbine (6) as claimed inclaim 1 or 2, in which the sealing element (44) is arranged betweenguide vanes (18) adjacent to one another in the circumferentialdirection (32) of the turbine.
 4. The turbine (6) as claimed in one ofthe preceding claims, in which the foot plates (21) each have a sideedge (56) bent away outwardly from the gas space (12), the sealingelement (44) being arranged between two side edges (56) of adjacentguide vanes (18).
 5. The turbine (6) as claimed in claim 4, in which theside edge (56) has substantially the same material thickness as theremaining foot plate (21).
 6. The turbine (6) as claimed in one of thepreceding claims, in which the front side (52) of the foot plate (21),said front side being directed toward the gas space (12), has, in theregion of the sealing element (44), a bearing surface (54) for thesealing element (44), said bearing surface being set back from the gasspace (12).
 7. The turbine (6) as claimed in claim 6, in which thesealing element (44) is flush with the foot plate (21).
 8. The turbine(6) as claimed in one of the preceding claims, in which, for cooling thesealing element (44), there is a flow path (58) for air between thesealing element (44) and the foot plates (21).
 9. The turbine (6) asclaimed in one of the preceding claims, in which a closed cooling system(62), through which a coolant is capable of flowing, is arranged in therear region of the foot plates (21) which faces away from the gas space(12).
 10. The turbine (6) as claimed in claim 9, in which the coolant iscapable of flowing over the rear side (74) of the foot plates (21) whichfaces away from the gas space (12).
 11. The turbine (6) as claimed inclaim 9 or 10, in which an inflow duct (64) for the coolant is formedbetween an outer guide sheet (68) and a baffle sheet (70) which isarranged between the outer guide sheet (68) and the foot plate (21) andwhich has flow orifices (72) toward the foot plate (21), a return-flowduct (66) for the cooling medium being formed between the baffle sheet(70) and the foot plate (21).
 12. The turbine (6) as claimed in claim11, in which the baffle sheet (70) is supported on the foot plate (21)via a supporting element (76).
 13. The turbine (6) as claimed in claim11 or 12 and 4, in which the baffle sheet (70) is fastened to thebent-away side edge (56) of the foot plate (21) and the guide sheet (68)is fastened, in particular, to the baffle sheet (70).
 14. The turbine(6) as claimed in one of the preceding claims, in which the sealingelement (44) is arranged between foot plates (21) adjacent to oneanother in the circumferential direction (32), and foot plates (21)adjacent to one another in the axial direction (8) are assigned in eachcase a further sealing element (80) which connects the foot plates (21)to one another in a staple-like manner on their rear sides (74) facingaway from the gas space (12).